feat(lsp): wire diary/auto_toc/links_space_char/list_margin; drop client-side keys

Consume several per-wiki config keys that the server deserialized but
ignored, and remove keys whose effect is purely client-side:

- diagnostics: re-publish open-doc diagnostics on
  didChangeConfiguration so a link_severity change takes effect
  immediately; fix the single-key unwrap in apply_change so a minimal
  `{ diagnostic: {...} }` payload isn't mistaken for a namespace wrapper.
- auto_toc: rebuild an existing TOC section on save (new
  ops::toc_rebuild_edit, no-op when the page has no TOC).
- diary index: honour diary_header, diary_sort and diary_caption_level
  when rendering the diary index body.
- links_space_char: apply on rename so spaces in the link target and
  the on-disk path become the configured glyph (default " " = verbatim).
- list_margin: thread the per-wiki value into render_page_html.
- remove nested_syntaxes, maxhi and diary_start_week_day from the server
  config: nested-syntax and heading highlighting are client-side, and
  the weekly diary is ISO-week based so a custom week start has no clean
  server-side meaning.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/nuwiki-lsp/src/export.rs

@@ -200,6 +200,7 @@ pub fn render_page_html(
     today: DiaryDate,
     cfg: &HtmlConfig,
     wiki_extension: Option<&str>,
+    list_margin: i32,
     extra_vars: HashMap<String, String>,
 ) -> std::io::Result<String> {
     let date_str = match doc.metadata.date.as_deref() {
@@ -224,7 +225,7 @@ pub fn render_page_html(
         vars.insert(k, v);
     }
 
-    let mut r = HtmlRenderer::new();
+    let mut r = HtmlRenderer::new().with_list_margin(list_margin);
     if let Some(ext) = wiki_extension.filter(|e| !e.trim_start_matches('.').is_empty()) {
         // Strip the wiki extension from page links before the default resolver
         // turns them into `.html` URLs, so `[[todo.wiki]]` → `todo.html` rather